But if the laptop hangs after resume, you may want to try
different values for hw.acpi.sleep.vbios (see acpi(4)).

Yeah, I tried 0, 1 and 2. None result in a resuming laptop. :-/

I experience the same problem with my laptop: lock-up after
resume. Disabling usb(4) in userconf makes this problem go away.
I filed a PR (kern/46931). Does your laptop also resume fine
(or at least without lock-up) when usb(4) is disabled?
Grégoire
p.s. My laptop used to resume fine (except for the backlight)
back in june 2011.